Christina was all too familiar with the desperation behind her incessant thoughts. Despite having her husband snoring softly at her side, she felt a deep sense of exclusion and isolation, stranded in a circadian limbo, trapped between the world of waking and the world of sleep.

She wasn't alone. At that very moment, in the seclusion of their own bedrooms, hundreds of millions of people in the industrialized world shared her ordeal. In simple numbers, sleep disorders are the most prevalent health concern of our times. A recent National Sleep Foundation poll found that 76 percent of American adults reported at least one symptom of a sleep disorder at least a few nights every week or more. The majority of these individuals struggle with insomnia: difficulty falling asleep, staying asleep, or obtaining healthy, restorative sleep. In any given year, from 30 to 40 percent of the adult population has insomnia. It's commoner in women and increases with age, medical problems, and psychiatric disorders. It's extremely common among adolescents, too.

Insomnia isn't simply about sleep loss—it's also about losing our dreams. Like many of my insomnia clients, Christina reported that she hardly ever remembered her dreams. Much of what we consider sleep loss is actually dream loss, leaving us at least as dream deprived as we are sleep deprived. To make matters worse, so many commonly used substances and medications interfere with normal dreaming. Using everything from alcohol to antidepressants and aspirin to tranquilizers, millions of people unknowingly suppress their dream lives nightly.

But our bodies and minds need to dream and will struggle to do so. Dreaming plays a critical role in consolidating learning and memory, facilitating emotional healing, assisting in problem-solving, and promoting creativity. Jung believed that the chronic suppression of dreams was a factor in cancer. Animal and human experiments that selectively inhibit dreaming result in a highly pressured dream rebound, displacing deep sleep and predisposing us to nightmares and insomnia.

Jonathan, a recently widowed and still grieving 52-year-old attorney, was morbidly obese, diabetic, and clinically depressed. Referred to me for chronic insomnia, which was increasingly interfering with his productivity, he acknowledged that he never dreamed. He routinely worked late into the evening, was able to fall asleep quickly, but could stay asleep through the night only with the aid of sleeping pills. Though he didn't know it, his medical problems and depression were likely linked to his chronic sleeplessness. Compelling evidence suggests that chronic sleep loss is a critical factor in a broad range of health concerns, including an increased risk for viral infections, obesity, diabetes, cardiovascular disease, and even cancer.

When I questioned Jonathan about the onset of his depression, he realized it trailed his insomnia by 8 to 10 months. The link between sleep and mental health is critical and complex. Approximately 80 percent of people with psychiatric disorders struggle with disturbed sleep. Insomnia, especially the inability to maintain sleep through the night, has long been known to be a classic symptom of depression. In recent years, sleep scientists have confirmed that it is itself a major cause of depression. In fact, a year of insomnia is the single strongest predictive factor for clinical depression.